Stabilized petroleum wax



Filed Jan. 26; l1955 Ovv mm QN SEQ United States Patent O STABILIZED PETROLEUM WAX Charles F. Duchacek, Long Island City, N. Y., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Application January 26, 1955, Serial No. 484,155

4 Claims. (Cl. 106-Z70) This invention has to do with the stabilization of petroleum products against the harmful elfects of oxidation and deterioration with use. More particularly, the present invention is primarily directed to the stabilization of mineral oil fractions, and particularly petroleum wax fractions, by the use of a novel combination of compounds which together exert a synergistic stabilizing effect.

As is well known in the art, petroleum waxes-and particularly parain waxes-oxidize readily. Oxidation takes place at elevated temperatures, for example, oxidation occurs when the wax is kept in a molten condition in open tanks. Also when parafn waxes are dried by airblowing ICC acid darkens when exposed to light. Stearic acid is generally applied as an outer coating to such materials as candles to stiften the latter vas well as impart the initial whiteningeect. It will be appreciated that light stability of candles is an important feature, because samples of candles oftentimes are displayed in showwindows.

It has now been discovered that the 'aforesaiddeleterions effects of oxidation can be counteractedfby a combination of additives which together behave synergistically'; One of the additives is generally regarded as the anti'- oxidant and the second of the additives is generally designated as they synergist. Here, it has been found that tertiary butylated hydroxyanisoles,otherwise known as Sustane, and related materials behave asvantioxidants.V In combination therewith is the synergist, stearyl citrate l and related materials. Each of these materials is used at temperatures of the order of 170 F. to 210F., an

offensive rancid odor generally develops. However, even at relatively low temperatures, as at 65-80" F., solid paraiin waxes can develop a rancid odor in prolonged storage. In addition, paraffin waxes when undergoing oxidation darken considerably in color. y

Inasmuch as petroleum waxes rare used in the compounding of pharmaceutical specialties, such as ointments, itis necessary that they be free of disagreeable odors. Still other uses for parafn waxes requiring substantially odor-free materials include: -food coatings, paper and cardboard food containers, milk containers, grease-proof paper, frozen-food wraps, fruit-wrap papers and the like. It is apparent, then, that if paraffin waxes are to be suitable for such uses it is necessary to shield them from oxygen or its is necessary to make them resistant to oxidation. Obviously, it is diflicult-if not economically impracticalto shield paran waxes from the atmosphere when using or storing the same, In addition, it will be recognized that toxicity is a major factor with waxes used for bread wrappings, milk cartons and the like. Toxicity l is of no moment when waxes are used for candles.

Methods hitherto proposed for making paraffin waxes resistant to oxidation have generally proven inefficient or n excessively expensive. For example, two such methods which have not been entirely successful are: (l) treatment with steam to drive off volatile organic acids, and,

(2) filtration through clay to remove acids by adsorption;

This problem has also been approached through the either color deterioration or the development of ka rancidodor, but these additives generally do not stabilize the` Wax against both of these deleterious effects. PropylA Several additives have been used withV However, such additives as have been.

gallate is an example of one material used for this purpose;

Another is a tertiary butylated hydroxyanisole, which has been sold under the commercial name of Sustane.

Waxes have also been treated to improve their color. One such approach to this problem has been to incorporate substantial amounts yof stearic acid with the 'vt/ax. vFor example, 15% by' weight of stearic acid hasbeen used commercially with parain wax. Initially stearic acid has a Awhitening effect on the Wax. However, stearic in relatively small concentrations. h

It is an object of this invention, therefore, toprotect materials susceptible to oxidation' against thegeneral effects of oxygen whether in storage or in use. `It is a primary object of this invention to protect wax and related hydrocarbon fractions against the vdeleterious effects of oxidation, in particular 'to protectvsuch materials against color and odor deterioration. Another object is to provide a product resistant to oxidation when stored at elevated temperatures. Still another object is' the provision of a product resistant to oxidation when exposed to light for relatively long periods of time. It is anotherV object of this invention to further improve wax and stearic acid blends. i

Another important object of this invention is to provide a new and novel composition of matter comprising a synergistic combination of materials. Other'objects of this invention will be apparent from the following idescription ofthe invention'. t l 'Y As indicated above, the'antrioxidant contemplated herein is a'hydroxyanisole containing an alkyl group of at least four carbon atoms, preferably from four to about eight carbon atoms. Tertiary butylated hydroxyanisoles such as f OCHs'. CI)CH3 C(CHa)s C(CHa)a are preferred herein, particularly mixtures of such isomers.

The synergist contemplated here comprises an alkyl ester of citric acid wherein the esterifying group or groups is a hydrocarbon solubilizing group. Outstanding of such esters is tristearyl citrate. Generally, the esterifying group for citric acid contains at least about twelve carbon atoms. It will be understood that from one to three of such groups can: be present in the ester, and that mixtures of such mono-, diand tri-esters can be used.

The antioxidant and synergist, described above, can beincorporated simply in a hydrocarbon product such as a petroleum wax. The additives are added to wax and stirredinto the same, in which they are readily dispersed. It has been found that temperature has some effect on the ease with which the additives become readily dispersed in the wax. In general, it is recommended that the wax be heated to a temperature of about to 180 F., whereupon the additives are added and stirred or mixed into the hot wax. The concentration of the Vantioxidant and of the synergist are so small that little difculty is encountered in dispersing or mixing the same in the wax. The antioxidant is generally used in concentrations from about 0.00005 to about 0.1% of the wax, preferably from about 0.0001 to about 0.005%. Correspondingly, the

aigseope-e 3 synergist is usually present in amounts ranging from 0.00005 to about 0.1% by weight, with preference to amounts ranging from 0.0001 to about 0.005%.

kI-Ieat stability of wagt'v and wax containing various additives is shown in the'fgure attached hereto Fcontaining' al bar graph. In" this instance, the wax and wax blends were stored in contact with iron in ,an oven at 200 F. and were periodically sampled forl color andodor ratings. The `wax used was a 12S-127 F. melting point, rened pa'ran wax. The odor tests were conducted in the following manner: AA small quantity of the wax sample was shaved into a clean,.o'dorless container. The container was sealed and allowed to .stand for at least onehour before it was reopened and the wax sample sme1led., Onesample was prepared4 as indicated foreach observerbecause repeated openingV of the container allows the Aodor to be dissipated. Theodor of the Ywax is rated in the followingA manner: 1 noj odor; 1.5 ,very slight odor; 2 mild odor; 3, moderateodor; 4 strong odor. An arithmetical average of ratings of the observers is taken as the nal result. t t

vReferring to thebar graph, it willwbeseen that the blank wax hasv astability of only two days. When a small amount of Sustane is added to the wax, the stability improved to four days. It is Ato be noted that small amounts of citric acid and tartaric acid do not improve further the wax` containing Sustane'. Y Opposed to these results, are the results obtained with a combination of Sustane and stearyl citrate; the resulting producthas a stabilityk of twenty-five days. This is entirely unexpected since stearyl citrate used alone in the wax will provide a stability of only two days, and Su'stane alone will provide a stability of only four days. Thus, the combination of Sustane and stearylrcitrate, on a theoretical basis, would be only about six days, instead of the twenty-five days actually found by experimentation.

Tristearyl citrate was used in the tests shown by the bar graph, and in the tests shown hereinbelow.

Oftentimes in' commercial operations, wax is stored over water rather than in a dry tank. It has been found thatwax stored over water is less stable than wax stored in a dry tank. Wax samples and Wax containing; additives were made up and were tested inthe following 4. manner. One samplewas added to a beaker wherein iron nails were present. Another sample was added to a beaker, 100 grams of wax sample being so added, together with 100 grams of water. Iron nails were then 5 added to the latter. These beakers were then stored at 180 F. Results of such tests are set below in Table I. The Saybolt color wasdetermined by the method of ASTM designation D`153T (see' ASTM Standards on Petroleum Products and Lubricants, November 1954 edition,`page'93).

TABLE I Average .Sayblti Color v Variables Days Of e l1:5-0dor Before After Effect of Stearyl Citrate Concentration In V Presence of Sustane (0.0002%): f e

0.0025 sa +,30 t v+ 28 +30A I +27 2'7' '+30' +211Y 29 +30 +26 Analysis of variables effectingv the light stability'uof paraflin wax', in the presence of antioxidants'wh'enstored in thev Fade-OlMeter for 96 hours, is provided in Table II below:

Additional heatv stability results are provided in 'liable III below. These results were obtained by subjecting wax and wax-additive blends at 180 F. in` contactV With iron for various periods of time.

TABLE DI Storge at 180 F. in contact with iron Steal-y1 .y v ,v ,Fade--lideter, Sustene, Citrate, Wax' Days Saybolt Color 96 HoursExposure Percent Percent Dry Over of 1'.5 Saybolt Color By By Wax Water Odor Weight Weight Before After Before l' After YES- 5 +30 +30 +30 +17 Yes. 1 +30 +30 0. 0025 Yes- +30 15 30 17 0. 0025 Yes- 55 +30 +14 i--- 0. 0002 Yes-- 57 +30 +17 +30 +22 0. 0002 Yes.- 53 +30 +16 0. 0025 YeS- 7 30 30 `30 30 0. 0025 Yes.-. 3 +30 +30 jl.- 0. 0002 Yes. 7 +30 +30 +30 +30 0. 0002 Yes.-. 7 +30 +30 0.0002 Yes- 24 -l-'ao '26 30 21 0. 0002 Yes--- 18 +30 +26 -I1-.-- i-.- 0. 0025 Yes 37 +30 30 +30 +28 0. 0025 Yes- 37 +30 23 which follows below.

127 F. (M. P.) parain wax when stored at 200 F. in contact with iron Percent y .Percent Days of Odor Days Saybolt Color Antioxidant By Synergist By +30 f of 1.5 Weight Weight Saybolt Odor Color Before After Before After 3 l. 5 4. 0 2 +30 +30 0. 0025 4 1. 5 1. 5 42 +30 -1 0.0025 Stearyl Citrate 0.01 25 1. 5 l. 5 42 +30 +24 0.0025 Isopropyl Citrate, 0.01 14 1. 5 1. 5` 32 +30 +22 0.0025 Citric Acid 0. 0025 4 1. 5 1. 5 14 +30 +22 0.0025 Tai-tario Acid 0. 005v 4 1. 5 1. 5 15 +30 +0 In Table V given below, additional heat stability erally used for whitening and stiffening the candles. The results are shown. Here, the heat stability of dry parain effect of Sustane and stearyl citrate of waX-stearic .acid wax and paratlin wax oatingoverwater .was determined blends is demonstrated below by the results set out at 180 F. in contact with iron. in Table VT.

TABLE v Days of Odor Y rSayboli: Color Antioxidant Percent Synergist Percent Dry Wax +30 Days By By Wax Over Saybolt 1.5

Weight Weight Water Color Before After Odor Before After Stearyl Citrate.. 10 1.6 4.0 7 +30 +30 Sustane 6 1. 5 1. 5 20 +30 +23 3 1.5 1.5 10 +30 +26 19 1.5 1.4 24 +30 +26 Inspection of results set out in Table V reveals that, TABLE VI in keeping with earlier ndings, wax is more suitable when stored in the dry condition, rather than when stored Eect of antioxidants o" wax'stearic acid blends 15% over Water. In this connection, it will be noted that stemc md the stability of dry Wax is ten days as opposed to five for the Wet Wax when the standpoint of color is observed. Fade O Meter, 96 The odor stability of the dry Wax is ve days opposed Sustane, Stearyl Hours Exposure to one day for the wet wax. Some measure of improve- Percm Saybolt Color ment is realized with Sustane alone, when used in a con- Weight Bly 4centration of 0.0002%. Correspondingly, a small 65 Weght Before After amount `of improvement is realized with stearyl citrate alone. However, when Sustane and stearyl citrate are 'j' g used together, a large and unexpected degree of improve- 0.0002 +20 +13 ment is realized. This is particularly pronounced in the 'jig case of a dry Wax. A lesser Improvement is obtained 0.0002 +22 +20 with a combination of the additives, when the wax sample is stored over water.

As indicated earlier, wax used for candles and the Additional tests on parain waX-stearic acid blends, like generally contain an outer coating comprising a together with parafn Wax, are shown in Table VII blend of wax and stearic acid. The stearic acid is gellgiven below.

TABLE VH Eect of antioxidant concentration upon the light stability of paran wax and parayjn wax-stearic acidl blends stored in the Fade-O-Meter for 96 h ours Stearyl 96 Hours Sustane, Citrate, Wax Hours Exposure Percent Percent Wax stearic +30 Saybolt Color y By Alone Acid Saybolt `Weight Weight Colorl e Before A ter types. Stabilization of solid hydrocarbons of the aliphatic 'series ranging 20 carbon atoms to about 35 carbon atoms is'V a'primary object of this invention.

1. 1Iydrocarhon` waxicontainngfrom about 0.00005 to about 0.1 percentfby,` Weight. of ,an hydroxyanisole containing a saturated alkylV group of at least four carbon aton1sandv from about 0.00005 to about 0.1 percent .by weightrof an alkyl ester of citric acid containing.v ,at least. oneV straight cha-insaturatedl allgylY groupv containing vvat least about twelve carbon atoms.

2. Hydrocarbon wax containing from about 0.00005 i .to about 0.1 percent by Weight of -a'tertiary` butyl hy` tion contemplated herein is directed tofthe stabilization of fatty oils, marine oils, vegetable oils and the like. In the iield of hydrocarbons, the invention is pointed to the stabilization of fully refined or semi-rened waxes derived from petroleum, Ozokerite and shale oils of Vall jdroxyanisole and from` about 0,00005 to-about 0.1Y perf cent by weight of'tristearyl citrate. Y

3. Paraflin- Vwax containing from about 0.00005 to about 0.1 percent by'Weight/of' a tertiary butyl. hydroxyanisole and VfromfaboutY 000005- toY about 0.1 percent by weight of stearyl citrate.

4. Parain wax containing from about 5 to about 40 percent by weight lof stearic acid, from about 0.00005 to=Y about 0:1'- percent by'weight of aftertiary butykliydrox- Y yan isole,..andffrorrry about 0,000.05:V to about 0.1 percent by weight of. stearyl citrate..

References Cited in the le of this patent UNITED STATES PATENTS 2,518,678. Gooding et al. Aug. 15, 1950 2,677,616 Hall May 4, 1954 2,633,694 Hoffman et al. July 13, 1954 2,704,746 Chenicelgl Mar. 22, 1955 72,715,073V v Lowry H Aug. 9, 1955 2,741,563 Robertson Apr. l0, 1956 25772: H5111 ::.,.:.r::'t,.f NOV' 27 1956 Hall Nov. 12, 1957 UNITED STATES PATENT QEEICE CERTIFICATE 0F CORRECTION Patent No., 298605,065 November ll, 1958 Gnarles E., Duenaeek.

It is hereby certified that error appears in the printed specification of thev above numbered partenil requiring correction and that the said Letters Patent should read as corrected below.

Column l5 line 429 for "its isn read m it is en; eolumn '7g line 23l strike out "combinations of materials contemplated herein, andu and insert the same after "The" in line 24g same columnc Signed and sealed this 10th day of February 1959o SEAL) tteSt KARL Ho XLINE ROBERT C. WATSON Attesting Ocer Commissioner of Patents 

1. HYDROCARBON WAX CONTAINING FROM ABOUT 0.00005 TO ABOUT 0.1 PERCENT BY WEIGHT OF AN HYDROXYANISOLE CONTAINING A SATURATED ALKYL GROUP OF AT LEAST FOUR CARBON ATOMS, AND FROM ABOUT 0.00005 TO ABOUT 0.1 PERCENT BY WEIGHT OF AN ALKYL STER OF CITRIC ACID CONTAINING AT LEAST ONE STRAIGHT CHAIN SATURATED ALKYL GROUP CONTAINING AT LEAST ABOUT TWELVE CARBON ATOMS. 